The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air/fuel (NF) mixture within cylinders to drive pistons that rotatably turn a crankshaft and generate drive torque. Operation of the engine (e.g., air/fuel ratios, fuel and spark timing, intake and exhaust valve timing, etc.) may be controlled based on various parameters. The parameters may be determined based on pressures within the cylinders. For example, an engine control module (ECM) may determine an indicated mean effective pressure (IMEP), a location to peak pressure (LPP), and percentages of air/fuel mixtures burnt in the cylinders (or burnt mass within the cylinders) at various crank angles (e.g., crank angle (CA)10, CA50, and CA90). The IMEP, the LPP and the percentages of burnt mass may be determined based on detected pressures within the cylinders.
Cylinder pressure sensors may be used to directly detect pressures within the cylinders of an engine. During operation, signal outputs of the cylinder pressure sensors can drift over time. As a result, the output signals can become saturated during LOW or HIGH pressure conditions. For example, a cylinder pressure sensor may have an operating output voltage range of 0.5V-4.5V. The cylinder pressure sensor may be initially setup such that 0.5V corresponds to a lowest pressure to be measured by the sensor (e.g., during an intake or exhaust stroke) and 4.5V corresponds to a highest pressure to be measured by the sensor (e.g., at the end of a compression stroke). Due to drifting, the output of the sensor may be saturated LOW such that pressures greater than the lowest pressure provide a voltage output of 0.5V. As another example, the output of the sensor may be saturated HIGH such that pressures less than the greatest pressure provide a voltage output of 4.5V. As a result, the output signal generated by the cylinder pressure sensor can become inaccurate over time. This can negatively affect engine parameter determination and control of engine operation.